add support for android

JNI_VERSION_1_8 isn't defined in android ndk for some reason so we
change that

Author: alexytomi

.github/workflows/ci.yml

@@ -55,6 +55,8 @@ jobs:
         target:
           - os: ubuntu-latest
             type: linux
+          - os: ubuntu-latest
+            type: android
           - os: ubuntu-latest
             type: windows
           - os: macos-latest
@@ -82,6 +84,7 @@ jobs:
 
       - name: Build
         run: |
+          export NDK_HOME=$ANDROID_NDK_HOME
           chmod +x buildSrc/scripts/build.sh
           buildSrc/scripts/build.sh ${{ matrix.target.type }}
 

buildSrc/scripts/build.sh

@@ -97,6 +97,28 @@ case "$VTYPE" in
         fi
         echo "Universal library created at /tmp/imgui/dst/libimgui-java64.dylib successfully"
         ;;
+    android)
+        echo "Running Gradle task for Android..."
+        ./gradlew imgui-binding:generateLibs -Denvs=android -Dfreetype=false
+        if [ $? -ne 0 ]; then
+            echo "Gradle task for Android failed"
+            exit 1
+        fi
+
+        echo "Checking if the generated SO files exists..."
+        check_file_exists /tmp/imgui/libs/arm64-v8a/libimgui-java64.so
+        check_file_exists /tmp/imgui/libs/armeabi-v7a/libimgui-java64.so
+        check_file_exists /tmp/imgui/libs/x86/libimgui-java64.so
+        check_file_exists /tmp/imgui/libs/x86_64/libimgui-java64.so
+
+        echo "Copying the generated SO files to the destination directory..."
+        cp /tmp/imgui/libs/* /tmp/imgui/dst
+        if [ $? -ne 0 ]; then
+            echo "Failed to copy SO files to /tmp/imgui/dst/libimgui-java64.so"
+            exit 1
+        fi
+        echo "SO files copied to /tmp/imgui/dst/<abi> successfully"
+        ;;
     *)
         echo "Unknown vendor type: $VTYPE"
         exit 1

buildSrc/scripts/vendor_freetype.sh

@@ -98,6 +98,9 @@ case "$VTYPE" in
         fi
         echo "Universal library created at lib/libfreetype.a"
         ;;
+    android)
+        # Skip freetype building for now because freetype repo doesn't seem to support android builds.
+        ;;
     *)
         echo "Unknown vendor type: $VTYPE"
         exit 1

buildSrc/src/main/groovy/tool/generator/GenerateLibs.groovy

@@ -32,6 +32,7 @@ class GenerateLibs extends DefaultTask {
     private final String[] buildEnvs = System.getProperty('envs')?.split(',')
     private final boolean forWindows = buildEnvs?.contains('windows')
     private final boolean forLinux = buildEnvs?.contains('linux')
+    private final boolean forAndroid = buildEnvs?.contains('android')
     private final boolean forMac = buildEnvs?.contains('macos')
     private final boolean forMacArm64 = buildEnvs?.contains('macosarm64')
 
@@ -103,7 +104,8 @@ class GenerateLibs extends DefaultTask {
         }
 
         // Generate platform dependant ant configs and header files
-        def buildConfig = new BuildConfig('imgui-java', tmpDir, libsDirName, jniDir)
+        String soFileName = !forAndroid ? 'imgui-java' : 'imgui-java64' // Android generates libimgui-java.so otherwise which isn't expected
+        def buildConfig = new BuildConfig(soFileName, tmpDir, libsDirName, jniDir)
         BuildTarget[] buildTargets = []
 
         if (forWindows) {
@@ -118,6 +120,12 @@ class GenerateLibs extends DefaultTask {
             buildTargets += linux64
         }
 
+        if (forAndroid) {
+            buildTargets += new BuildTarget(Os.Android, Architecture.Bitness._32, new String[] {"**/*.c"}, new String[0],
+                new String[] {"**/*.cpp"}, new String[0], new String[0], "", "-O2 -Wall -D__ANDROID__", "-O2 -Wall -D__ANDROID__",
+                "-lm -Wl,-z,max-page-size=0x4000 -stdlib=libc++ -lc++_shared");
+        }
+
         if (forMac) {
             buildTargets += createMacTarget(Architecture.x86)
         }
@@ -137,12 +145,15 @@ class GenerateLibs extends DefaultTask {
             BuildExecutor.executeAnt(jniDir + '/build-windows64.xml', commonParams)
         if (forLinux)
             BuildExecutor.executeAnt(jniDir + '/build-linux64.xml', commonParams)
+        if (forAndroid) // Contrary to the name, this builds all four ABIs (arm64, arm, x86, x86_64)
+            BuildExecutor.executeAnt(jniDir + '/build-android32.xml', commonParams)
         if (forMac)
             BuildExecutor.executeAnt(jniDir + '/build-macosx64.xml', commonParams)
         if (forMacArm64)
             BuildExecutor.executeAnt(jniDir + '/build-macosxarm64.xml', commonParams)
-
-        BuildExecutor.executeAnt(jniDir + '/build.xml', '-v', 'pack-natives')
+        // Exclude android because android packages into aar, not jar
+        if (!forAndroid)
+            BuildExecutor.executeAnt(jniDir + '/build.xml', '-v', 'pack-natives')
 
         if (forWindows)
             checkLibExist("windows64/imgui-java64.dll")

imgui-binding/src/main/native/jni_jvm.cpp

@@ -10,7 +10,7 @@ namespace Jni
 
     JNIEnv* GetEnv() {
         JNIEnv* env;
-        jint res = jvm->GetEnv((void**)(&env), JNI_VERSION_1_8);
+        jint res = jvm->GetEnv((void**)(&env), JNI_VERSION_1_6);
         assert(res == JNI_OK);
         return env;
     }